1. FIELD OF THE INVENTION
This invention relates generally to fluid handling and more particularly to fluid handling processes involving pressure control.
2. DISCUSSION OF THE PRIOR ART
Presently, air brake systems for towed vehicles generally comprise two arrangements. First, there is the type of system utilizing a single service reservoir for providing a source of pressurized air to all the service brake chambers and a single emergency or parking reservoir for supplying pressurized air to all the parking brake chambers. Second, there is the type of system utilizing more than one service reservoir each providing a souce of air for operating some of the service brake chambers and a single parking reservoir for supplying pressurized air to all the parking brake chambers.
In the first type of system, should a failure occur in that system such as a depletion of air pressure in the service reservoir through leakage or otherwise, there is no available air pressure for communication with the service brake chambers thus rendering those brakes inoperative. Also, should a failure occur in the first system parking reservoir through leakage or otherwise, the resultant loss of air pressure communicating with the parking brake chamber would cause an undesirable automatic application of the parking brakes and also prevent subsequent release of the applied brakes.
In the second type of system, there is a slight advantage over the first system in that, should a failure occur in the second system such as a depletion of air pressure in one of the two service reservoirs, there would still be some air pressure available in the other of the two service reservoirs for communication with some of the service brake chambers to effect partial braking. However, should a failure occur in the single parking reservoir, the resultant loss of air pressure communicating with the parking brake chambers would cause the abovementioned undesirable automatic application of the parking brakes. It would therefore be of benefit to have a service and parking brake system offering more than single service reservoir capability to provide at least partial service braking in the event of failure in one of the service systems and also offering more than single parking reservoir capability so that, in the event of failure in one of the parking reservoirs, there would still be air pressure communication with the parking brake chamber to prevent the undesirable automatic application of the parking brakes.